The five 261s I have stockpiled at the moment run the gamut from 54 to at least 59, maybe newer. Two of them have the big oil ports and I have two big canister "full flow" oil filters stashed away in case I want to go to a poor quality filtering method for some reason. It's possible that I might run both a full flow filter to strain out the rocks, marbles, and bowling balls, and a 1 micron bypass filter to really clean up the oil a little at a time.

Any "stock" engine is just a blank canvas for an engine building "artiste" to use to paint a masterpiece with. The good ones look totally original on the outside and hide all the improvements internally. They're called "sleepers"!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!